Backpack



FIG. 1 is a perspective view of the backpack being worn by a person, with the person shown in phantom and all straps, buckles and zipper assemblies of the backpack also shown in phantom;

FIG. 2 is rear view of the backpack;

FIG. 3 is a front view thereof;

FIG. 4 is a right side view thereof, the left side view being a mirror image of the right side view;

FIG. 5 is a bottom view thereof; and,

FIG. 6 is a top view thereof;

The dashed lines on the backpack are understood to represent stitching.

The person, buckles, straps, and zipper assembly shown in phantom are for illustrative purposes only and form no part of the claimed design. 

The ornamental design for a backpack, as shown and described. 